Half-Life 2 - Gateways Mod

This is a single player Half Life 2 mod, set entirely outside of city 17. it features:
6 levels of action, exploring a range of locations (from an underground facility to fighting alongside the combine on an alien world to floating color-coordinated cubes)
Non-linear level progression- you start near a nexus of gateways, and may choose the order in which to progress through the levels
A musical score (a total of 8 tracks)
Some new abstract textures (see image 3)
Challenging gameplay- this mod is meant for those who have already completed Half Life 2.